test(ts-plugin): split find-all-references and rename-symbol e2e tests into per-behavior cases (#379)

* test(ts-plugin): split find-all-references and rename-symbol e2e tests into per-behavior cases

Continue the e2e test refactor started in #378. Each test now owns a minimal
fixture and asserts a single behavior, organized by the .d.ts/mapping pattern
under test. Also revisit go-to-definition.test.ts so all three feature test
files share the same describe structure.

This is the second PR of a multi-PR series (see #378 for the first PR).

Shared describe structure (group 1 differs by feature, groups 2-5 are common):

- Group 1: feature-specific Volar.js auto-mapping
  - go-to-definition: jumps to the top of a CSS module file (5 tests)
  - find-all-references: finds all references to the styles binding (1 test)
  - rename-symbol: (none — module specifier rename is sendGetEditsForFileRename
    territory and styles binding rename is core TS behavior, not ts-plugin's)
- Group 2: <feature> a local token (TS-side trigger, 3 tests)
- Group 3: transitively resolves a re-export to its source declaration (3 tests)
- Group 4: <feature> from a CSS-side class declaration (1 test, newly added)
- Group 5: <feature> from a CSS-side @value ... from binding (3 tests)

Per-file totals:
- go-to-definition: 15 tests x 2 namedExports variants = 30
- find-all-references: 11 tests x 2 namedExports variants = 22
  (was 17 cases sharing one fixture inside a single test.each)
- rename-symbol: 10 tests x 2 namedExports variants = 20
  (was 13 cases inside a single test.each, only namedExports: false)

rename-symbol now also covers namedExports: true via describe.each.

* refactor(ts-plugin): move test/builder.ts under src/test/ to match other packages

* test(ts-plugin): rename multi-declaration test to a scenario qualifier

Other test names in the same describe blocks describe a trigger position
or fixture shape (e.g. "from styles.<token> access"), but this one was
phrased as a result ("returns all declarations ..."). Drop the verb so
the name reads as a scenario qualifier on the parent describe and stays
consistent across all three feature files.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: mizdra